The teenage gunman who executed a NSW Police Force employee was lauded as a "hero of the Islamic people" on a social media page, which was taken down late on Monday at the request of the police.

Fifteen-year-old Farhad Khalil Mohammad Jabar was killed during a shoot-out with special constables outside police headquarters in Parramatta on Friday.

The high school student walked up behind police accountant Curtis Cheng, 58, and shot him in the back of the head before being fatally shot on the footpath.

On one of the Facebook pages that have emerged since the shooting, the teen has been labelled the "hero of Parramatta".

Some the people who commented on the page appeared to be sympathisers with far-right, anti-Islamic groups, including Rise Up Australia and Reclaim Australia, suggesting the page may have been a ploy to use the death of Mr Cheng to whip up anti-Islam sentiment.

However it remained unclear who set up the Facebook page, or why they did so.

"Hero of the Islamic peoples he will be gratly (sic)," one post reads on the Facebook page.

"Death to the evil police state of Australia who killed this young child all he is guilty of was being muslim!!"

Asked about the page, NSW Police Deputy Commissioner Nick Kaldas said it was disappointing.

"Just as disappointing as the right-wing extremist material," he said.

Police have also called on Facebook to take action over anti-Islamic pages, including one calling for retaliation attacks against mosques and imams.

"It's very disappointing to see that group and many other groups join them in really abhorrent calls for violence" Mr Kaldas said.

"It is not the answer. It won't solve anything and I urge anyone who has any influence over those people to stop that from happening."

Mr Kaldas warned if a person did advocate violence against a particular group it could constitute a crime.

He could not say for certain what was on the young shooter's mind but it was clear he was "disturbed".

Police have appealed to parents to keep talking with their children to prevent the radicalisation of young people.

"I would urge any parent who has concerns about their child being radicalised to sit and talk to them, show them love," Mr Kaldas said.

"Show them affection; show them a home environment that pulls them away from abhorrent influences.

"Where there is a vacuum, where no one is talking to kids about values, morals, what's right and wrong, someone else will come in and fill that vacuum."